The present invention relates generally to aircraft brakes, and in particular to aircraft brake assemblies that are convertible from a first type of heat sink to a second type of heat sink.
Steel heat sink aircraft brake assemblies have proven to be economical, reliable, and desirable for aircraft that fly relatively short distances. Steel heat sink aircraft brake assemblies are still state of the art in the aerospace industry. Such brake assemblies typically include either steel rotor or stator disks and a corresponding plurality of friction material rotor or stator disks. Carbon-carbon composite heat sink aircraft brake assemblies are increasing in their usage as the size of commercial aircraft and their flying distance has increased. As disclosed in co-owned Massing et al. U.S. Pat. No. 5,321,876, commercial aircraft flying long distances or long hauls may increase revenue and/or reduce operating costs by utilizing the significant weight benefits offered by a carbon-carbon composite heat sink as compared to a generally heavier steel heat sink. However, if an aircraft with carbon-carbon composite heat sinks is scheduled to fly a short haul, the use of such heat sinks may not be cost effective. Massing et al. U.S. Pat. No. 5,321,876 discloses a method of converting aircraft brake assemblies from a first heat sink to a second heat sink, wherein different piston bushing assemblies, backing plate connectors and heat shields are utilized for the respective heat sinks. It is highly desirable that an aircraft brake assembly suitable for utilization of either a carbon-carbon composite heat sink or a steel heat sink can be easily converted from one heat sink to the other. It is an object of the present invention to simplify the method of converting aircraft brake assemblies, and thus avoid the distinct disadvantages of converting or retrofitting an existing brake assembly from a carbon-carbon composite heat sink to a steel heat sink which could result in a heavier steel aircraft brake assembly than a brake assembly designed originally to be only a steel aircraft brake assembly. With the present invention, an airline would be able to utilize a method for converting the aircraft brake assembly and thus can order a group or fleet of aircraft suitable for long and short hauls, with the long haul aircraft utilizing a carbon-carbon composite heat sink brake assembly while the short haul aircraft utilize a steel heat sink aircraft brake assembly. Other reasons for converting may include airline maintenance cost and capabilities, fluctuating fuel costs or flight weight limitations. Also, should changes in aircraft scheduling occur, the particular type of heat sink utilized in the brake assemblies can be converted easily to a different type of heat sink. It is highly desirable that a convertible brake assembly contain common parts in order to the reduce the number of parts and inventory, and that corrosion resistance of parts be improved to effect the enhanced reliability and useful life of the parts. Also highly desirable is that vibrations in the brake assemblies be minimized to reduce the possibility of damage to parts of the assemblies, and that appropriate thermal barriers be present to prevent or reduce heat transfer. Finally, it is highly desirable that the convertible brake assembly of the present invention have the capability of being changed to a different convertible brake assembly, such as one or more of the convertible brake assemblies disclosed in copending U.S. patent application Nos. 09/322,255 and 09/335,243 and U.S. Pat. No. 5,926,932, in order to offer the aircraft operator the advantages described above for carbon-carbon and steel aircraft brake assemblies. The present invention provides solutions to the above problems by providing an aircraft brake assembly designed as original equipment to be convertible from a first heat sink of one of carbon and steel brake assemblies to a second heat sink of the other of carbon and steel brake assemblies, the aircraft brake assembly for connection with a surrounding wheel via rotor disks of the respective heat sink, each heat sink including a pressure plate disk, rotor disks, stator disks, and a backing plate disk, the brake assembly comprising the first heat sink, a torque tube connected with the stator disks of the first heat sink and including a backing plate with pad means for engaging the backing plate disk, a piston housing connected by means for connecting with the torque tube, and a spacer member, the piston housing having a plurality of piston bushing assemblies with pistons located a distance from the pressure plate disk, the first heat sink having an overall axial length substantially filling an axial space between the pistons and pad means, comprising the steps of:
disassembling the piston housing, piston bushing assemblies, torque tube, connecting means, spacer member, and first heat sink, and
assembling the second heat sink, torque tube, piston housing with piston bushing assemblies, connecting means, and spacer member, the piston housing having longer piston bushing assemblies, wherein the second heat sink has a shorter axial length than the first heat sink and the longer piston bushing assemblies position the pistons at substantially said distance from the pressure plate disk of the second heat sink.